Color photographic element protected against fading and method of applying protective film thereto



United States Patent 3 Claims. in. 96-48 The present invention relatesto an anti-fading layer by means of which color photographs may beprotected against the colorafading action of daylight, in particular ofsunlight.

It is known that an improved fastness to light may be obtained byapplying or incorporating a substance which absorbs in the long-waveultraviolet range into one or more layers of a photographic materialcontaining gelatin. It is further known that water-soluble substancesabsorbing in the ultraviolet region may be incorporated into thefinished print by an anti-fading bath or that alternatively the finishedprints may be coated with an anti-fading layer containing a substancewhich absorbs in the ultraviolet region.

Ultraviolet radiation-absorbing compounds (referred to hereafter also asUV-absorbents and antifading agents) which are used for photographicpurposes are generally the same compounds that are used in the plasticsindustry, for example, hydroxybenzophenone, monoazo compounds,xenylamine (4-biphenylamine), fluorenone, benzalmethylphenyl hydrazone,cyanine dyes and N,N-bis- (sulfosalicyloyl)benzidine (which is alsoknown as 4,4- bis(sulfosalicyloylamino)diphenyl), derivatives of higheraromatic hydrocarbons, etc.

These compounds may be used in their original form or in the form of adiffusion-resistant water-soluble derivative containing a fatty acidradical. It is also known to apply such water-soluble UV-absorbentstogether with a film-forming substance in the form of an aqueoussolution or dispersion onto a photographic material or to apply asolution of suitable UV-absorbents and film-forming substances inorganic solvents onto color photographs.

However, all these methods have various disadvantages; for example, thewater-soluble and diffusion-resistant absor-bents have their molarabsorption reduced by the fatty radical, and thus provide insufiicientprotection. Other water-soluble compounds which are not resistant todiffusion may diffuse from the surface into deeper layers and even downto the paper support, thereby reducing the protective action on thesurface. Moreover, these substances may easily be washed out by asubsequent washing. Water-insoluble absorbents applied by means offilm-forming substances are usually not sufficiently soluble infilm-forming substances and tend to crystallize therein. They cantherefore be used only in relatively low concentrations. Finally,film-forming substances have varying and usually poor adhesion togelatin and can therefore peel off by the action of water or bymechanical action.

It is among the objects of the present invention to provide anti-fadinglayers for color photographic images, thus providing images which haveimproved stability against the action of artificial light and daylight.Other objects will be apparent from the following description.

We have found that substituted hydroxybenzophenones serve as very usefulanti-fading agents in combination with the copolymers described below.The ultravoilet radiation-absorbing compounds or antifading agents thatare 3,215,530 Patented Nov. 2, 1965 used in accordance with ourinvention have the following general formula:

| l R OH In this formula R and R which may be alike or differentrepresent a tertiary butyl or isopropyl group, R is hydrogen or analkoxy group having 1-5 carbon atoms and R represents hydrogen or analkyl group, having 1-5 carbon atoms.

These anti-fading agents can be readily prepared according to the methoddescribed in Example 1 hereinafter.

Among the benzophenone derivatives which can be used are the following:

2,4'-dihydroxy-3 ',5 '-di-tertiary-butyl-benzophenone2,4'-dihydroxy-3',5-di-isopropyl-benzophenone 2,4'-dihydroxy--tertiary-butyl-5-isopropyl-benzophenone 2,4'-dihydroxy-4-methoXy-3',5'-di-tertiary-butylbenzophenone 2,4-dihydroxy-4-methoxy-3 ',5-di-isopropylbenzophenone 2,4-dihydroxy-4-ethoxy-3 ',5'-di-isopropyl-benzophenone 2,4'-dihydroXy-4-propoxy-3,5-di-isopropyl-benzophenone 2,4-dihydroxy-4-pentoxy-3',5'-di-isopropylbenzophenone4,4-dimethoxy-2-hydroxy-3',5'-di-tertiary-butylbenzophenone4,4'-diethoxy-2-hydnoxy-3 ,5-di-tertiary-butylbenzophenone4-butoxy-4-methoxy-2-hydroxy-3 ',5'-di-tertiarybutyl-benzophenone4-methoxy-4-butoxy-2-hydroxy-3 ',5 -di-isopropylbenzophenone.

A great advantage of the anti-fading agents of this invention resides inthe features that they have a very good solubility in the copolymersdescribed below which are used as binding agents for the anti-fadinglayers. Thus these compounds do not crystallize even when the layer iscompletely dried.

It is possible to obtain a clear, transparent layer which contains up to30 percent of the UV-absorbent and which affords excellent protectionagainst light. Accordingly, it is possible to obtain adequate protectionby application of relatively thin anti-fading layers.

Binding agents containing the anti-fading agents described hereinbeforewhich can be used include copolymers of maleic anhydride with vinylalkyl ethers, the alkyl groups of which contain up to 5 carbon atoms.Vinyl alkyl ethers which may be used in the production of suchcopolymers with maleic anhydride include, for example, vinyl n-butylether, vinyl isobutyl ether and vinyl propyl ether. Said copolymers maycontain the two components in a molecular ratio between 05:1 and 1.5: 1of maleic anhydride to vinyl alkyl ether preferably, however, about 1:1.The preparation of the copolymers is accomplished according to Example1, using a conventional polymerization catalyst.

Such copolymers are easily soluble in organic solvents such as ethylacetate or ketones.

These anti-fading layers show an excellent adhesion to the gelatin layerof the color photographic image which is probably due to the anhydridegroupings of the binding agent. It is a particular advantage of theselayers that the adhesion power is independent of the moisture content ofthe gelatin layer, which may vary within wide EXAMPLE 1 23 g. of afilm-forming agent consisting of the copolymer of vinyl butyl ether andmaleic anhydride whose preparation is described hereinafter aredissolved in 230 m1. of distilled diethyl ketone with moderate heating.After cooling, 7.0 g. of 2,4'-dihydroxy-3,5'-di-tertiary butylbenzophenone prepared as described hereinafter are added and thesolution is filtered through a cloth. This solution is cast onto colorphotographs. The resulting anti-fading layer having a thickness ofbetween 2 and 20 microns shows no blushing even after several weeksstorage.

When the 2,4"dihydroxy-3',5'-di-tertiary butyl benzophenone in theforegoing example is replaced by each of 2,4'-dihydroxy benzophenone and2,4-dihydroxy-3,5'-diethyl benzophenone the resulting films deposited onthe color photographs show blushing and the formation of patches ofprecipitated benzophenone compound as early as 1 to 2 weeks of storageat room temperature.

Preparation of the copolymer 30 g. of distilled vinyl butyl ether, 36 g.of maleic acid anhydride and 0.07 g. of benzoyl peroxide [C H CO) O aredissolved in 100 ml. of dry and pure methyl acetate. 20 percent of thesolution is heated to the boiling point of the mixture in a nitrogenatmosphere on a water bath at 60 to 70 C. and the remaining 80 percentis added while stirring and refluxing gently for 4 hours. After additionis complete, stirring and refluxing is continued for 2 more hours.Thereafter, the solution is stirred into benzene, whereupon thecopolymer precipitates. The product is purified by redissolving it inmethyl acetate and reprecipitating by stirring into benzene.

Preparation of 2,4'-dihydroxy-3,5'-di-tertiary butyl benzophenone 200 g.of aluminum chloride are added in portions to a solution of 206 grams of2,6-ditertiary butyl phenol and 170.4 grams of 2-methoxybenzoyl chloridein 700 cc. of nitrobenzene with cooling. The temperature should notexceed +15 C. Thereafter, the mixture is stirred for 2 hours at roomtemperature. After adding 600 cc. benzene and refluxing for 1 /2 hours,the reaction product is decomposed with cold water. The organic phase isextracted by shaking several times with dilute sodium hydroxide, wherebythe 2,4'-dihydroxy-3,5'-ditertiary butyl benzophenone is extracted inthe form of its water-soluble sodium salt. After acidifying thissolution and recrystallizing the precipitated crystals from ligroin, ayield of 204 g. is obtained. Melting point 125127 C.

EXAMPLE 2 An anti-fading layer is produced as described in Example 1except that the dihydroxyditertiary-butyl-benzophenone is replaced by anequimolar quantity of 2,4-dihydroxy-3,5'-di-isopropyl benzophenone.

Color photographic images coated with this layer as described in Example1 remain unaltered after storing for 1-2 weeks at room temperature.

EXAMPLE 3 An anti-fading layer is prepared as described in Example 1except that the dihydroxy-ditertiary-butylbenzophenone is replaced by anequimolar quantity of2,4'-dihydroxy-4-methoxy-3,5'-di-isopropyl-benzophenone.

Color photographic images coated with this layer as described in Example1 remain unchanged after storing for several weeks at room temperature.

EXAMPLE 4 An anti-fading layer is prepared as described in Example 1except that the dihydroxy-ditertiary-butylbenzophenone is replaced by anequimolar quantity of2,4'-dihydroxy-4-methoxy-3',5'-ditertiarybutylbenzophenone.

Color photographic images coated with this layer as described in Example1 remain unchanged after storing for several weeks at room temperature.

EXAMPLE 5 An anti-fading layer is prepared as described in Example 1except that the dihydroxy-ditertiary-butylbenzophenone is replaced by anequimolar quantity of 4,4'-dimethoxy-2-hydroxy-3 ,S'-ditertiarybutylbenzophenone.

Color photographic images coated with this layer as described in Example1 remain unchanged after storing for several weeks at room temperature.

What is claimed is:

1. A method of preventing image degradation in a finished colorphotographic element comprising a support and superposed thereon aplurality of developed and fixed photographic emulsion layers containingcoupleddye images, at least one of the said dye images being subject tofading by the action of ultraviolet radiation, which comprises applyingto the said photographic element from a nonaqueous solution a film of afilm-forming copolymer of maleic anhydride and a vinyl alkyl ether, thealkyl group of which contains up to 5 carbon atoms, in a molecular ratiobetween 05:1 and 1.5:1 of maleic anhydride to the vinyl alkyl ether,containing an effective amount of an ultraviolet radiation-absorbingcompound of the group consisting of hydroxy-substituted benzophenoneshaving the formula MI ZQaQa.

in which R and R are each a radical of the group consisting of isopropyland tertiary butyl,

R is a radical of the group consisting of hydrogen and alkoxy containingup to 5 carbon atoms, and

R is a radical of the group consisting of hydrogen and alkyl containingup to 5 carbon atoms.

2. A finished color photographic element comprising a support andsuperposed thereon a plurality of developed and fixed photographicemulsion layers containing coupled-dye images, at least one of the saiddye images being susceptible to fading by the action of ultravioletradiation, and superposed on the top layer thereof, a film offilm-forming copolymer of maleic anhydride and a vinyl alkyl ether, thealkyl group of which contains up to 5 carbon atoms, in a molecular ratiobetween 0.5 :1 and 1.5 :1 of maleic anhydride to the vinyl alkyl ether,and containing an effective amount of an ultraviolet radiation-absorbingcompound of the group consisting of hydroxy-substituted benzophenoneshaving the formula R on in which R and R are each a radical of the groupconsisting of isopropyl and tertiary butyl,

R is a radical of the group consisting of hydrogen and alkoxy containingup to 5 carbon atoms, and

R is a radical of the group consisting of hydrogen and alkyl containingup to 5 carbon atoms.

5 6 3. A finished color photographic element as defined in 3,008,99511/61 Hoeschele et a] 26045.95 claim 2 in which the film-formingcopolymer is a co- 3,050,500 8/62 Sherwood 26045.95 polymer of maleicanhydride and vinyl butyl ether in the 3,105,094 9/63 Hoeschele 26045.95molar ratio of about 1:1.

5 FOREIGN PATENTS References Clted the Examiner Canada UNITED STATESPATENTS 2 94 97 11 54 Grosser 96 4 HAROLD N- BURSTEIN, Examiner-2,719,086 9/55 Sawdey et a1 9611 NORMAN G. TORCHIN, Primary Examiner.2,875,053 2/59 Minsk 9684 10

1. A METHOD OF PREVENTING IMAGE DEGRADATION IN A FINISHED COLORPHOTOGRAPHIC ELEMENT COMPRISING A SUPPORT AND SUPERPOSED THEREON APLURALITY OF DEVELOPED AND FIXED PHOTOGRAPHIC EMULSION LAYERS CONTAININGCOUPLEDDYE IMAGES, AT LEAST ONE OF THE SAID DY E IMAGES BEING SUBJECT TOFADING BY THE ACTION OF ULTRAVIOLET RADIATION, WHICH COMPRISES APPLYINGTO THE SAID PHOTOGRAPHIC ELEMENT FROM A NONAQUEOUS SOLUTION A FILM OF AFILM-FORMING COPOLYMER OF MALEIC ANHYDIRDE AND A VINYL ALKYL ETHER, THEALKYL GROUP OF WHICH CONTAINS UP TO 5 CARGON ATOMS, IN A MOLECULAR RATIOBETWEEN 0.5:1 AND 1.5:1 OF MALEIC ANHYDRIDE TO THE VINYL ALKYL ETHER,CONTAINING AN EFFECTIVE AMOUNT OF AN ULTRAVIOLET RADIATION -ABSORBINGCOMPOUND OF THE GROUP DONSISTING OF HYDROXY-SUBSTITUTED BENZOPHENONESHAVING THE FORMULA